Between October and December, U-T San Diego military reporter Jen Steele and photographer Peggy Peattie spent dozens of hours on the streets of San Diego and at local aid agencies to meet young homeless veterans and hear their stories.

When night comes to the San Diego streets, some of the people sleeping on piled-up blankets once bedded down in fighting holes in Iraq or Afghanistan.

They are the leading edge of a new generation of homeless veterans, some of whom saw combat, came back changed and now have begun a downward spiral, not unlike veterans of earlier eras.

Experts say that young Iraq and Afghanistan-era veterans aren’t yet on the streets in large numbers. They are couch surfing with buddies. They are living with girlfriends or boyfriends. They are camping in their cars.

And San Diego aid agencies are seeing young faces at their doors.

At Veterans Village of San Diego, 39 Iraq or Afghanistan veterans are in a residential program for people battling drugs and alcohol and who need help to stay off the streets. The average age is 29.

The number of post-Sept. 11 veterans living at St. Vincent de Paul Village’s downtown program has jumped to 14, after hovering at two or three for several years.

The San Diego VA estimates that 1,753 veterans are homeless in this region. Officials don’t know how many of those are fresh from Iraq or Afghanistan service. If the local picture follows national trends, it would be about 8.8 percent, or 154 people.

These young fighters are challenged in a way that average people aren’t. Veterans say they forever carry the memories of war.

Post-traumatic stress disorder — the severe form of what’s sometimes called combat stress or the World War I term “shell shock” — is found in up to one in five recent combat veterans.

“I would tell you that whenever we deal with homelessness, several issues come up. Some of it has to do with depression, substance abuse. Someplace in here PTSD is operative,” said Veterans Affairs Secretary Eric Shinseki. “Some of this has to do with education and jobs and employment.”

One former Navy SEAL returned home to San Diego in 2007 and dove into a whiskey bottle to numb his PTSD. A few years later, he ended up living in his truck, with a criminal charge pending. His story of struggle, and rehabilitation, is part of this package.

Experts say that money usually means the difference between a roof overhead and life on the street for veterans who are vulnerable. High unemployment — at 12 percent for all post-Sept. 11 vets and 29 percent for young male veterans in 2011 — has taken a toll.

Joshua Lopez looked like any other 20-something standing around at the Old Town Transit Center, smoking and joking with his buddy in October.

Then, he flipped over his arm. And there was the tattoo. A Marine Corps eagle, globe and anchor, a purple heart in the center, taking up most of his left forearm.